Pro Football Focus - Who is the hardest hitter in NFL history?
Plain and simple: Ray Nitschke was the Packers
TOUGHEST PLAYER IN NFL HISTORY - Ray Nitschke
The Top Defensive Player in the History of Every NFL Franchise, News, Scores, Highlights, Stats, and Rumors
Ray Nitschke Pro Football Hall of Fame
Toughest Football Players in NFL History
The dirtiest players in NFL history – Orange County Register
The NFL ain't what it used to be: Today's game stinks (1983) - Sports Illustrated Vault
Bart Starr was the toughest football player who ever lived - ESPN
Toughest Football Players in NFL History
Greatest Green Bay Packers players of all time: Ray Nitschke